1. Field of the Invention
The present invention relates to a method for the in situ bioremediation of nitrogenous contaminants; more particularly to the use of one or more microorganisms to metabolize nitrogenous energetic materials present in a medium, such as soil and water.
2. Discussion of the Related Art
The manufacturing, use, and disposal of highly nitrogenated energetic materials have resulted in the contamination of soil and groundwater with potentially hazardous compounds. The generally high nitrogen content of such energetic materials makes the remediation of these compounds difficult and costly. Such materials include, for example, organic nitroaromatics, inorganic nitrates, organic nitramines, and organic nitrate esters. Nitramines, although apparently extremely rare in nature, are produced in significant quantities by the chemical industry and comprise, for example, an important class of energetic materials having applications as explosives and propellants. There are concerns regarding the environmental fate of nitramines due to their relative persistence and therefore there exists a need for a means of removing such contaminants from the environment without producing other undesirable pollutants.
Examples of organic nitroaromatics include TNT, hexanitrostilbene (HNS), hexanitroazobenzene (NAB), diaminotrinitrobenzene (DATB), and triaminotrinitrobenzene (TATB). Examples of organic nitramines include RDX, HMX, nitroguanidine (NQ), and 2,4,6-trinitrophenylmethylnitramine (tetryl). Examples of organic nitrate esters include PETN, nitroglycerine, and ethylene glycol dinitrate. A sample inorganic nitrate includes ammonium nitrate. RDX (1,3,5-trinitro-1,3,5-triazine is both an energetic material and a toxic substance and is currently the most important military explosive in the United States. The manufacture, handling and disposal of RDX can all lead to the contamination of the environment with RDX. The EPA has determined that RDX is a possible human carcinogen and that RDX can cause seisures in humans and animals when large amounts are inhaled or eaten. A large number of sites worldwide, including both soil and ground water, have been found to be contaiminated with RDX. These sites include manufacturing, storage, load assemble and pack, and demilitarization facilities. It has now become necessary to remediate these contaminated sites. The current method for soil remediation of RDX involves removal, incineration and replacement of the treated soil. Such a process is extremely expensive and cumbersome. Removal of RDX from ground water involves extensive and expensive filtration processes.
The use of microorganisms to remediate these sites is a potentially attractive alternative to incineration and filtration. Examples of bioremediation have been disclosed in U.S. Pat. Nos. 6,274,368 to Nicklin et al., using novel bacteria and U.S. Pat. No. 6,066,772 using a combination of anaerobic and aerobic processes. Bioremediation of energetic materials has also been described for use in ordinance the in U.S. Pat. No. 6,120,627 to Badger, et al.
The present invention provides a bioremediation process for the reduction of environmental contamination of nitrogenous energetic compounds, such as RDX.